Investigations of hot-dip galvanized dual-phase steel (DP600+Z) sheet metal on selectively oxidized tool steel surfaces under dry deep-drawing conditions

Abstract

Abstract As reported in previous studies conducted within the priority program 1676 “Dry forming - Sustainable production through dry machining in metal forming”, selectively oxidized tool surfaces represent a promising approach for the realization of a dry forming process. For the transfer of the findings to an actual industrial deep drawing process, the choice of sheet material is of great importance. The present study reports investigations on hot-dip galvanized dual-phase steel that was deep-drawn with selectively oxidized tools made from hardened 1.2379 tool steel. The data are compared to the deep-drawing behavior of electrolytically galvanized deep-drawing steel, which was used as a reference. The applied oxide system consisted of α-Fe2O3 and was generated in an tailored atmosphere with controlled partial pressure of oxygen. A specially developed modular deep-drawing tool was used for the deep-drawing tests, which allowed carrying out cup-drawing tests in which parts of the drawing ring featured different oxidation conditions. The differently set load cases on the drawing ring were then evaluated and examined with respect to the resulting surface properties of the component produced. The changes in the surface morphology prior to and after deep drawing were analyzed using high resolution analysis and the interactions between tool coating and sheet metal were examined. The results obtained provided information about the deep-drawing properties of the sheet metal materials and confirmed the advantages of α-Fe2O3 tool coating used as a low-friction separating layer for use in dry deep drawing.